(1) Field of Invention
The present invention relates to a tunable filter and, more particularly, to a miniature tunable filter having high power and low loss capabilities.
(2) Description of Related Art
Tunable filters, typically used for multiband telecommunication systems, radiometers, and wideband radar systems, are electric filters in which the frequency of the passband or rejection band can be varied by adjusting its components. Several filter designs exist in the prior art. For instance, miniature ceramic filters use high dielectric constant ceramic materials to reduce the size of the filters; however, current designs are fixed frequency and have limited radio frequency (RF) power handling. Additionally, machined filters, such as Air Core filters, are large in size and are not suitable for mobile or lightweight applications. Furthermore, varactor tuned filters have high loss and a limited tuning range, especially at frequencies greater than 500 megahertz (MHz). Finally, Yttrium Iron Garnet (YIG) tuned filters have high direct current (DC) power consumption, limited RF power handling due to saturation of the ferrite material used, and have a typical frequency range of 2-40 gigahertz (GHz).
Thus, a continuing need exists for a miniature tunable filter which can be tuned over a wide range of frequencies and has low loss and high power capabilities.